Process of crystallizing sugar.



no. $90,014. Patented Dec. 3|, l90l.

H. CLAASSEN. PROCESS OF CRYSTALLIZING SUGAR.

(Application filed Feb. 16, 1901.)

(No Model.)

Unrrn STATES nrnr OFFICE.

HERMANN OLAASSEN, OF DORMAGEN, GERMANY.

PROCESS OF CRYSTALLIZING SUGAR.

SPECIFICATION forming part of Letters Patent No. 690,014, dated December 31, 1901.

Application filed February 15, 1901. $erial No. 47,511. (No specimens.)

To all whmn it may concern:

Be it known that I, HERMANN CLAASSEN, a subject of the King of Prussia, German Emperor, and a resident of Dormagen, Rhenish Prussia, German Empire, have invented new and useful Improvements in Processes of Orystallizing Sugar, of which the following is a specification.

This invention has for its object to provide a process for regulating the supersaturation ofthe molasses ofamasse-euiteproducedfrom impure saccharine solutions, which molasses surrounds the crystals while crystallization in motion is carried on, such regulation being effected by a predetermined addition of water in such a manner that according to the temperature and the purity of such sugar solution the most favorable conditions are kept up for causing the crystallization of the sugar and its depositing on the existing crystals and for preventing the formation of small new crystals as far as such prevention is practically required. The degree of said supersaturation will be different fromthat is, lower thanthat prevailing in the boiling of the original solutions. In the latter case a proportionately higher supersaturation may pre- Vail, because with the boiling in the vacuumpan the crystallization or deposition upon the existing crystals will take place much more rapidly than with the cooling-down crystallization and because the viscosity which prevents crystallization will not assert itself at high temperature, and, finally, because the motion of the mass is a very thorough one, in consequence of which the temperature will be uniform throughout the entire mass. In the case mentioned the sugar which separates in great quantities at the high supersaturation of the solution will only enlarge the existing crystals and will form no new grain or crystals. Now, according to the process of this invention, the addition of water during crystallization of the masse-cuite in the crys tallizing apparatus is regulated in such manner that at every stage of the crystallizing of said masse-cuite a predetermined degree of supersatuation of the molasses in which the crystals are contained is kept up, said massecuite being continuously or periodically agitated and cooled down. Cooling down of the mass in the crystallizer should, however,take place slowly. To stir the mass rapidly by mechanical means in order to cause a thorough mixing will not do, because in this case, especially with very impure molasses, the mass will become foamy. A partial greater cooling may take place in the mass at the walls of the crystallizer,such parts of the mass thereby becoming supersaturated to a higher degree than the warmer parts of the mass. This will particularly take place at the beginning of the crystallizing process in the crystallizer when the masse-cuite is still hot. By the cooling down the supersaturation of the molasses will materially be increased, because by the influence of the non-sugar substances and by the viscosity of the mass, which will increase during the cooling,the power in the masse-cuite to prevent crystallization Will become so great that the entire mass of sugar which with the decreasing temperature is contained in the saccharine solution in an amount exceeding that corresponding to such temperature (supersaturation) will not find time and opportunity to deposit upon the existing crystals. Thus under all these circumstances in the masse-cuite the formation of new grain will easily take place, which never develops to such sizes that it might be recovered in the centrifugal machine. Thus the yield of sugar is reduced as it is to a great extent expelled by centrifugal action with the final molasses,and, further, the quotient of the final molasses separated by centrifugal action is increased, and centrifugal separation is interfered with by the formation of a film on the sugar in the centrifugalseparator. Accordingtothepresent invention a predetermined degree of supersaturation of the molasses is to be kept up during the entire operation of crystallizing, so as to obtain a proper crystallizing and to avoid the above-mentioned defects. The supersaturationthat is, the quotient or degree of supersaturation-has to be so selected for each period of the crystallizing operation that it does not arrive at such a height or limit as to cause formation of new crystals. It is a matter of experience that the formation of new crystals in the sugar solutions of tion which takes place by the formation of a crystal depositv of sugar upon the existing crystals.

I prefer to proceed as follows: After boiling in the vacuum-pan has been completed water is drawn in at this stage in order to bring the supersaturation of the sugar solution down to the desired quotient, and then the mass is allowed to run into the crystallizers, in which a further addition of water in proportion to the cooling takes place. In explanation I would state that the term quotient of supersaturation is defined as the quotient obtained by dividing the quantity of sugar dissolved in one part of water in the concentrated sugar solution by the quantity of sugar contained in one part of Water at the same temperature in the saturated solution of sugar. As to the addition of water, it has to be taken into consideration that the supersaturation during the cooling down of impure sugar solutions will rise in a fargreater proportion than with the cooling of pure sugar solutions, since the state of saturation will change in quite a dilferent manner in the two cases. Not only the temperature, but also the quality and especially the quantity, of the non-sugar substances will be of great influence upon the state of saturation. The solubility of the sugar will be much greater in impure sugar solutions than in pure ones, such solubility increasing with the quantity of non-sugar present. Again, the influence of a given quantity of non-sugar upon the solubility of the sugar is the greater the more elevated the temperature is. Thus, for instance, in a saturated solution of beet-root sugar of about sixty-three purity there are 5.8 parts of sugar dissolved in one part of water at centigradethat is, 1.6 times as much as in a pure saturated solution of the same temperature-whereas the same sugar solution of about sixty-three purity is saturated at 50 centigrade if it contains in every part of water 3.4 parts of sugaror 1.3 times as much sugar only as is dissolved in a pure sugar solution saturated at 50 centigrade. These figures, which indicate how many times more sugar is dissolved in impure saturated solutions in one part of water than in pure ones of equal temperature, "are the quotients of saturation. The following table indicates the quotients of saturation for sugar solutions of about sixty-two to sixty-four purity:

There are dissolved in one part of Wate1- In my new process the supersaturation by addition of water is so regulated that corre-' sponding to the purity of the original sugar solution and to the decreasing temperatu rethe quotient of supersaturation remains between 1.05 and 1.25. This treatment of the second inasse-cuite must, according to the conditions of crystallization in motion, require a longer period than with the masse-cuite of the first products, because the second masse-cuite will crystallize more slowly,owing to the influence of non-sugar matters. Therefore the desired purposeinviewnamely,athoroughcrystalli zation-will not be arrived at if the addition of water should take place during a rapid cooling within a few hours. Such cooling should be so slow that the temperature for centrifugal separation will be obtained only after sixty hours or even later. Since the dissolving power of the impure sugar solution will, as above stated, depend also upon the purity of the same and of the masse-cuite, the addition of water will differ according to the purity of said solution or masse, because the dissolving power of the sugar solution de creases with an increase of its purity, and thereby the quotient of saturation becomes a different one. Such quotient being a lower one with pure solutions than with impure ones, the following points for the addition of water have to be taken into consideration: first, that the proportion of water contained in the molasses surrounding the crystals will in consequence of the crystallizing of the sugar have to increase, and that in a higher degree at the beginning than later on, because the relatively pure sugar solutions, which of course are purer in the beginning than later on when sugar has been separated and deposited on the existing crystals, will crystallize more rapidly; second, that the solubility of the sugar will decrease withthe falling temperature; third, that this decrease will take place in a greater proportion than with pure or relatively pure solutions, which pro portion is expressed by the quotients of supersaturation, and, fourth, that with the nearly uniform sinking of the temperature a definite progression in the quantity of the water to be added for each masse-cuite may be established if the purity and the contents of water of the molasses are known.

It must be especially stated that the object of this process is to obtain in the crystallizing apparatus a further crystallizing of the masse-cuite which has been emptied from the vacuum-pan into the crystallizer and to cause the molasses surrounding the crystals to deposit its sugar upon the existing crystals as far as possible, so that in the following separation of the solution from the crystals such solution is a final molasses. This process therefore very materially differs from those processes in which the sugar solution which surrounds the crystals is converted by boiling down and by addition of final molasses in the boiling apparatus into a final molasses from which no further amount of sugar can be separated by crystallization, and in which processes the soobtained massecuite is quickly cooled down in cooling apparatus provided with stirrers and diluting means are only added in order to have a-product readily capable of being treated in a centrifugal separator.

In order to illustrate the process which forms the subject-matter of the present application, the following example is given: A molasses of seventy-five purity issuing from a first product masse-cuite is by means of boil ing to grain crystallized to such a degree that at the emptying stage the molasses of the second masse-cuit-e possesses a purity of sixtyfive to sixty-seven. This second masse-cuite is let down into the crystallizing apparatus with the molasses containing eight and a half per cent. of water at a temperature of 93 Centigrade. The cooling down in this example is so regulated that a temperature of 45 centigrade is reached in four days. The term perature will sink as near as possible in the following manner: At the end of the first day to about 80 centigrade, at the end of the second day to about 70 centigrade, at the end of the third day to about 58 Centigrade, and at the end of the fourth day to about 45 centigrade. At 88 centigrade the addition of water is commenced with the following quantities: At 88 centigrade for every cubic meter of masse-cuite, 2.6 liters; at 84 centigrade for every cubic meter of masse-cuite, 2.6 liters; at 80 centigrade for every cubic meter of masse-cuite, 5.3 liters; at 76 centigrade for every cubic meter of masse-cuite, 5.3 liters; at 72 centigrade for every cubic meter of masse-cuite, 5.3 liters; at 68 centigrade for every cubic meter of masse-cuite, 5.3

liters; at 64 centigrade for every cubic meter of masse-cuite, 5.3 liters; at centigrade for every cubic meter of masse-cuite, 5.3 liters; at 56 centigrade for every cubic meter of masse-cuite, 5.3liters at 54 centigrade for every cubic meter of massecuite, 5.3

liters; at 50 centigrade for every cubic meter of masse-cnite, 5.3 liters; and at 45 centigrade for every cubic meter of masse-cuite, 5.3 liters. The mass will thus be at the end of the fourth day desaccharized down to purity of final molasses, and the final molasses,which is practically free from fine crystals, is ready for centrifugal separation, as it is only slightly supersaturated.

It is not a matter of necessity to exactly regulate the cooling down of the second massecuite in the manner above prescribed. It might be preferred, as soon as the temperature has sunk several degrees, to commence with the addition of the required quantity of water. This addition of water may take place continually during the entire period of cooling or periodically, as in the example shown. It must take place at all events early enough to avoid exceeding the desired quotient of supersaturation.

The following figures of proportion are given to illustrate how the addition of water may vary with masse-cuites of variable purity and different contents of water of the molasses while running off.

Liters. 8 per cent 7. 8.5 per cent. E) per cent.. 10 per cent Liters.

Liters.

In the accompanying drawings I have shown an apparatus suitable for carrying out my improved process;

Figure 1 is a longitudinal section of said apparatus. Fig. 2 is a cross-section thereof on line w as of Fig. 1, and Fig. 3 is a detailed end elevation of the device for admitting the heat-regnlatin g fluid.

The apparatus consists of a stationary drum A, having heads 00 m and provided with a jacket B, into which water or any other suitable heat-controlling medium may be admitted, said device comprising a pipe at, connected with the jacket B, and valves 12 b controlling connections to pipe a.

D is the outlet from the jacket B. I V

E is an aperture through which the massecuite is introduced into the drum A, and F is an opening through which the mass may be observed.

At the bottom ofthe drum is located an outlet G, provided with a valve controlled by a lever G. Within the drum is arranged axially a shaft H, carrying a worm-wheel J, which is rotated by a worm K. Stirrer-blades I are secured upon the shaft I-l within the drum A.

M indicates a thermometer which extends into the drum A, and N is a water-tank pro- ICO V'ided with a graduation N and connected with the interior of the drum A by a valved pipe 02. Through this pipe proper quantities of water are supplied during the cooling ofi 5 the mass, as hereinloefore referred to. I cla'i 1n-- ing thereto an increasing proportion of water in such amount as to keep the quotient of supersaturation between 1.05 and 1.25.

In testimony that I claim the foregoing as my invention I have signed my name, in presence of two witnesses, this 25th day of Janu- The method of crystallizing sugar from a ary, 1'901.

saccharine solution of a masse-cuite produced from impure saccharine solutions, which con- 1o sists in slowly cooling said solution while imparting motion thereto, and gradually add- 1 HERMANN OLAASS'EN.

Witnesses:

WILLIAM ESSENVVEIN, LUDWIG HIRT. 

